The invention relates to a tool for the production of cast components. In addition, the invention relates to a method for the production of such a tool, as well as a method, for the production of a cast component.
The present invention relates to the production of components, in particular gas turbine components, from nonferrous molten metals, in particular from titanium aluminum alloys, in particular from such materials with 43 to 48% percent in weight of aluminum which form an intermetallic phase by a casting method. During casting, molds, so-called casting molds, are used wherein the casting molds have an interior contour which corresponds to the exterior contour of the component to be produced. In principle a distinction is made between casting methods which use non-permanent casting molds and those which use permanent casting molds. With casting methods which use non-permanent casting molds only one component can be produced with one casting mold. With casting methods which use permanent casting molds the casting molds can be used more than once. So-called precision casting among others is one of the casting methods which use non-permanent casting molds. Reference is made here to gravity casting as an example of casting methods which use permanent casting molds. The present invention relates in particular to the so-called precision casting.
Precision casting uses according to the state-of-technology casting molds which are made of highly refractory ceramics. Production of a casting mold for precision casting roughly involves a first step during which a model is provided for the cast component to be produced later with the casting mold wherein the model has a shape similar to the cast component to be produced but with larger dimensions allowing for the measure of shrinkage of the casting material. This model is also called a component wax model. As defined by the state of technology this component wax model is preferably coated several times with a slurry material as well as sanded and if necessary subsequently backfilled so that the casting mold is either available in the so-called compact mold or in the so-called shell mold after the component wax model is melted off. After the component wax model is melted off the thus created, one-piece casting mold is fired. The still molten metal of the cast component to be produced can then be poured into the preferably hot casting mold wherein the produced cast component is dismantled from the casting mold after hardening. The casting mold is hereby lost.
As already stated the casting molds are made as per state of technology from highly refractory ceramic materials such as aluminum oxide, zircon oxide or yttrium oxide with additions of silicon dioxide. An appropriate slurry material is spread on a component wax model using a state-of-technology slurry method. However, casting molds containing additions of silicon dioxide are reactive and cause surface faults during the production of cast components from reactive nonferrous molten metals such as titanium alloys or also titanium aluminum alloys. This can cause surface faults, deviations in dimensions, cracks and the formation of so-called shrinkage cavities on the cast component to be produced. Thus the known state-of-technology casting molds are not suitable for reactive nonferrous molten metals.